Effect of Zn Interstitials on Enhancing Ultraviolet Emission of ZnO Films Deposited by MOCVD

ZnO films are grown on Si (111) substrates by a metal organic chemical vapor deposition method. Samples with different stoichiometric composition of Zn and O are obtained by varying II/VI molar ratio between 3 and 1/3 in precursors. The x-ray photoelectron spectroscopy and photoluminescence results show that the ultraviolet emission enhances with the increasing Zn/O composition ratio of the samples. It is suggested that the superfluous Zn atoms pile up at interstitial positions to form Zn interstitial defects. The radiated recombination of the coupling of free excitons with donor Zn interstitial enhances the ultraviolet emission of the samples.